I think they are the variable resistors or preset vertical trimmer potentiometers. I've fitted these in one of my boxes, the one marked 1m is 1 ohm and the other is 100 ohm. i got them from Mallinson Electrical.
Little tip change one then the other as easy to get muddled up as they look the same.
They are adjustable to set your depth, us a small terminal screw driver and car full not to force.
Cheers Arry